Making a removable bottom was reasonably simple. I cut eight smaller blocks approximately two inches square. Four of the blocks were attached to the inside of each enclosure, along the bottom edge, centered on the front, back, and sides to provide material for a screw to penetrate. Rubber feet were attached to the bottom panels, at each corner, one inch in from the edges. Using four long screws the bottom was secured to the cabinet. To assure an air tight seal, I placed foam Weather Strip on the bottom panel in a rectangular shape to match the base of the enclosure. Tightening the four long screws, centered on each edge into the smaller blocks mentioned above, compressed this seal nicely.